Falling into the unsea

[ajotatxe he/him]

I'm wondering what actually happens if you fall "eternally" into the unsea, assuming that it has no bottom, and that you can breath. You eventually die, of course. But why?

First I thought of thirst. In the Cognitive Realm, you don't sweat, but the resistance of the air (perceived like a very strong wind) could dehydrate you relatively soon.

But when you fall, air pressure increases very quickly. I have done the math with the barometric formula and I obtained 20 atm after falling 20,000 m (assuming a top speed of 200 km/h this would happen in a few minutes). I doubt that a human body can resist such a quick pressure change. On the other hand, the more dense air should slowen you a bit.

But the temperature of the 'air' increases with the pressure. With only 1.5 atm, the temperature increases by 50% in kelvin. That means about 170 celsius. This happens only after a fall of 3500 m, about a minute.

My conclusion is that you'd roast. Literally.

By the way. The internal heat of the deeper layers of the unsea should make it glow like a star. So actually, the unsea must have a bottom. Or it doesn't follow the Ideal Gas Law. Given that the temperature at Emberdark is all but steady, this seems likely. Barotrauma, then?

Edited August 12, 2025 by ajotatxe

[Treamayne]

1 hour ago, ajotatxe said:

I'm wondering what actually happens if you fall "eternally" into the unsea, assuming that it has no bottom, and that you can breath. You eventually die, of course. But why?

First I thought of thirst. In the Cognitive Realm, you don't sweat, but the resistance of the air (perceived like a very strong wind) could dehydrate you relatively soon.

But when you fall, air pressure increases very quickly. I have done the math with the barometric formula and I obtained 20 atm after falling 20,000 m (assuming a top speed of 200 km/h this would happen in a few minutes). I doubt that a human body can resist such a quick pressure change. On the other hand, the more dense air should slowen you a bit.

But the temperature of the 'air' increases with the pressure. With only 1.5 atm, the temperature increases by 50% in kelvin. That means about 170 celsius. This happens only after a fall of 3500 m, about a minute.

My conclusion is that you'd roast. Literally.

By the way. The internal heat of the deeper layers of the unsea should make it glow like a star. So actually, the unsea must have a bottom. Or it doesn't follow the Ideal Gas Law. Given that the temperature at Emberdark is all but steady, this seems likely. Barotrauma, then?

I do not think Physical Realm physics applies to Cognitive Realm geography/atmosphere. Shadesmar is a flat plane where geography only loosely correlates to the Physical Realm (sometimes) where Gravity does not cause curvature and shadows point toward the "sun" rather than away. I would be surprised if altitude (height or depth) caused any change in "pressure" until and unless the majority of Cosmere Sapients began believing it should work that way - and even then it would take a long time for such a change to occur. 

Hope that helps

[ajotatxe he/him]

5 hours ago, Treamayne said:

I do not think Physical Realm physics applies to Cognitive Realm geography/atmosphere. Shadesmar is a flat plane where geography only loosely correlates to the Physical Realm (sometimes) where Gravity does not cause curvature and shadows point toward the "sun" rather than away. I would be surprised if altitude (height or depth) caused any change in "pressure" until and unless the majority of Cosmere Sapients began believing it should work that way - and even then it would take a long time for such a change to occur. 

Hope that helps

Still, in the Rosharan subastral Kaladin and his companions could obtain water by condensation, a technique that, given that in Roshar there is plenty of fresh water, I doubt that Rosharans knew (a spren taught them how to do it).

The 'sun' of Shadesmar is something that I fail to understand. Shadows go to it, instead of from it. So, the lit side of an object is the one that is backwards. Then, if you want to read a book, you put it between you and the sun? Do other light sources, like fire, work the same way? And, if you sink into the sea of beads, you should see much light there, shouldn't you? And if the cognitive realm is flat, why can't this sun be seen from the other subastrals? Perhaps the inversion of shadows only applies to living beings from the Physical Realm and the lighting of the other objects is normal?

[Treamayne]

3 hours ago, ajotatxe said:

Still, in the Rosharan subastral Kaladin and his companions could obtain water by condensation, a technique that, given that in Roshar there is plenty of fresh water, I doubt that Rosharans knew (a spren taught them how to do it).

To be specific, they collect water from a Fabrial that is explained as using condensation - which may or may not be the entire truth (unreliable narrator happens). But moisture in the air isn't a factor in Shadesmar weather, either. 

OB CH 99:

Spoiler

Ico sighed and regarded him with a suffering expression. Very human in its nature. It seemed the look of a man talking to a child. The spren captain waved his hand, insistent, so Kaladin took a diamond mark from his pocket.

Cradling the sphere in one hand, Ico touched the glass bead he’d put in the fabrial. “This is a soul,” he said. “Soul of water, but very cold.”

“Ice?”

“Ice from a high, high place,” he said. “Ice that has never melted. Ice that has never known warmth.” The light in Kaladin’s sphere dimmed as Ico concentrated. “You know how to manifest souls?”

“No,” Kaladin said.

“Some of your kind do,” he said. “It is rare. Rare among us too. The gardeners among the cultivationspren are best at it. I am unpracticed.”

The ocean bead expanded and grew cloudy, looking like ice. Kaladin got a distinct sense of coldness from it.

Ico handed back the diamond mark, now partially drained, then dusted off his hands and stood up, pleased.

“What does it do?” Kaladin asked.

Ico nudged the device with his foot. “It gets cold now.”

“Why?”

“Cold makes water,” he said. “Water collects in that basin. You drink, and don’t die.”

Cold makes water? It didn’t seem to be making any water that Kaladin could see. Ico hiked off to survey the spren steering the ship, so Kaladin knelt beside the device, trying to understand. Eventually, he spotted drops of water collecting on the “branches” of the device. They ran down the metal and gathered in the basin.

Huh.

Note that Air in Shadesmar is "leakage" from the Physical Realm, but does not have or require an oxygen cycle (Shadesmar plants don't do that) or other PR properties. WoB:

Spoiler

Pagerunner

If you need to bring food into Shadesmar, why don't you need to bring air?

Brandon Sanderson

Y'know, we actually talked and thought about this. There are certain things I just decided for narrative reasons... I wanted Shadesmar to be travelable and I wanted it to be a real place, and so I just made air, I came up with kind of my own hacks. There are times I do this for narrative reasons. 

Let me give you an easier example. In the Mistborn books, and I've told people this before, I was working on speed bubbles. Slowing down time, speeding up time in a small little bubble around you, right? I went to Peter and I'm like, "This is what I'm going to do, what are the problems with this?" And he's like, "Well, redshift." Which means that basically you would be irradiating everyone with the light coming from inside the speed bubble. I'm like, "alright, we're just going to say that doesn't happen." This is where the line between for me science fiction and fantasy exists. When I'm building my story, I do try to have one foot in science with things like this. But I tend to work backward... A lot of science fiction starts with what we have now and extrapolates forward to [an] interesting, plausible premise. For my fantasy works, I start with some cool idea. And then I work backward in plausibility, trying to justify it. And we kind of meet in the center, but at the end of the day I am breaking the laws of thermodynamics, right? Just straight-up breaking laws-- I mean, we have our whole Realmatic Theory and stuff like that, but at the end of the day, I am trying to tell stories where certain extreme situations exist. Like, I bent over backwards to make the science of Roshar work with the greatshells, but at the end of the day, we still have to have a magical solution, right. To get beasties as big as we want to do, it doesn't matter how high your oxygen content is, if you've got .7 gravity or not, all these concessions we've made: the square-cube law says those things crush themselves. You just can't have things this big. And so we built in a magical solution. The spren creating this symbiotic bond is making it so these things don't crush themselves. 

And when I was looking at Shadesmar, there are a couple things-- what I want for the narrative is this place. I am going to work backward and try to make as many concessions and nods toward science as I can. But the air one, I just said "You know what? There's just gonna be air in Shadesmar. I am just gonna make it so that you can." I want you to be able to walk between the planets on Shadesmar, I don't want people to have to worry about bringing a Windrunner with them and plants or whatever to get oxygen. I'm just gonna make that the case. Your in-world answers, I'm like "Well, air kind of permeates and has escaped through and things," but really do we have an oxygen cycle there? We've got plants, but are they really--

The answer is, there is air in Shadesmar because I want there to be air in Shadesmar. 

JordanCon 2018 (April 21, 2018)

3 hours ago, ajotatxe said:

So, the lit side of an object is the one that is backwards.

<snip>

why can't this sun be seen from the other subastrals?

Nope. The light in Shadesmar is omnipresent and non-directional. All sides of a person or object are "lit." Other sources of light create shadows that work like the physical realm. The Shadesmar "sun" is visible from all Subastrals, but not always in the space between planets. 

Spoiler

RoW Ch 22:

Quote

The sky was black as midnight, only without stars. The sun seemed too distant, too frail, to properly light the place, though he wasn’t in darkness. He could easily see the small platform around them, which was the size of the control room. The sunlight illuminated the landscape, but strangely didn’t light the sky.

OB Ch 97:

Quote

He managed to reach the wall of the tower, where he might have expected the heat of the enormous fire to be oppressive. Instead, he could barely feel it. Notably, the flames caused his shadow to behave normally, extending behind him instead of pointing toward the sun.

M:SH Ch 1-1:

Quote

He was alive. Kind of.

He managed to look up. That same thick greyness shifted all around him. A nothingness? No, he could see shapes in it, shadows. Hills? And high in the sky, some kind of light. A tiny sun perhaps, as seen through dense grey clouds.

M:SH Ch 5-1:

Quote

He'd Hoped to have the sun back once Ruin vanished from the sky, but after walking far enough out, he seemed to leave his world behind—and the sun with it. The sky here was nothing but empty blackness.

 

 

3 hours ago, ajotatxe said:

Perhaps the inversion of shadows only applies to living beings from the Physical Realm and the lighting of the other objects is normal?

Nope - it is at least all Sapient beings, as Syl's shadow also points toward the Shadesmar Sun

OB Ch 91:

Spoiler

Syl didn’t make any noise as she approached, but he caught sight of her shadow coming up from behind—like other shadows here, it pointed toward the sun. She sat down on the lump of glass next to him, then thumped her head sideways, resting it on his arm, her hands in her lap.

Hope that helps

[alder24]

11 hours ago, ajotatxe said:

I'm wondering what actually happens if you fall "eternally" into the unsea, assuming that it has no bottom, and that you can breath. You eventually die, of course. But why?

First I thought of thirst. In the Cognitive Realm, you don't sweat, but the resistance of the air (perceived like a very strong wind) could dehydrate you relatively soon.

But when you fall, air pressure increases very quickly. I have done the math with the barometric formula and I obtained 20 atm after falling 20,000 m (assuming a top speed of 200 km/h this would happen in a few minutes). I doubt that a human body can resist such a quick pressure change. On the other hand, the more dense air should slowen you a bit.

But the temperature of the 'air' increases with the pressure. With only 1.5 atm, the temperature increases by 50% in kelvin. That means about 170 celsius. This happens only after a fall of 3500 m, about a minute.

My conclusion is that you'd roast. Literally.

By the way. The internal heat of the deeper layers of the unsea should make it glow like a star. So actually, the unsea must have a bottom. Or it doesn't follow the Ideal Gas Law. Given that the temperature at Emberdark is all but steady, this seems likely. Barotrauma, then?

What makes you think that there is any change in pressure or temperature in the Unsea? On Earth, this happens because of gravity - the higher you are, the less air is above you, thus pressure drops. We have no indication that the same thing applies to the Cognitive Realm. Shadesmar is weird and unintuitive, physics as we know it simply doesn't work there - it's the perception that is a dominant factor shaping Shadesmar. I see no reason to assume that the Unsea works like a typical physical atmosphere. And Starling does believe that she can be falling in it indefinitely without dying or getting crushed by the imploding wreckage, so I don't think we can compare the Unsea to a normal gas. IotE ch 54:

Quote

She had little doubt that the pilots would spare a moment, even during all the killing, to shoot at the Dynamic. Starling—indestructible but unable to transform into her winged form—could safely be allowed to fall through the darkness of the unsea until the crisis was over. Then she could be recovered from the still-plummeting wreckage, snatched from among the corpses of her friends.